Polishing media stabilizer

ABSTRACT

A polishing apparatus that employs a polishing media retention arrangement to prevent slippage or wrinkles in the polishing media during polishing. The polishing media is drawn against a support surface by a vacuum applied between the polishing media and the support surface. Also, a porous layer may be placed between the polishing media and the support surface to form dimples in the polishing media upon the application of vacuum. An alternative arrangement draws the polishing media against a carrier and the substrate to be polished.

TECHNICAL FIELD

[0001] The present invention relates to the field of polishing, andespecially to chemical mechanical polishing. More specifically thepresent invention is directed to improvements in retention of thepolishing surface and retention of polishing fluids during polishing.

BACKGROUND ART

[0002] Polishing a workpiece to produce a mirror-like, defect-freesurface has applications in many fields of endeavor. Such polishingprocesses have become extremely important and widespread, for example,in the fabrication of semiconductor devices. The critical step ofpolishing a semiconductive wafer or substrate is required at a number ofdifferent stages along the varied processes employed to fabricatesemiconductor devices.

[0003] Chemical mechanical polishing is rapidly becoming a technique ofchoice for polishing substrates, and particularly for use in themanufacture semiconductor devices on a wafer or substrate. The devicesare connected by a process generally referred to as metalization, inwhich connecting lines of metal, often aluminum or copper, are appliedby vacuum deposition or other suitable processes.

[0004] The performance level of semiconductor devices employing aconventional single metal layer connecting the devices is fast becomingunsuitable. Modern, high performance devices utilize multilevel metalinterconnections. Multilevel connections may be constructed bydepositing a dielectric or insulating layer over a first metal layer,etching via holes throughout the dielectric layer, and then depositing asecond metal layer which fill the via holes to connect with the firstmetal layer. These devices offer higher device density and shortenedinterconnection lengths between the devices.

[0005] Since each of these metal and dielectric layers have anappreciable thickness, the wafer substrate is left with a non-planartopography as the various layers are patterned on top of one another.This type of non-planarity is often unacceptable in high density devicesbecause the depth of field of the lithographic equipment that is used toprint the smaller line width circuits on the wafer does not have a depthof focus sufficient to compensate for even small variations in waferplanarity.

[0006] In addition to the non-planarity caused by the fabricated devicepatterns, in-process wafer polishing, or planarization, must account forvariations in overall wafer flatness as well. During the fabricationprocess, for example, the wafers may become bowed or warped.

[0007] In process polishing equipment, therefore, requires thespecialized ability to achieve global, uniformly planar wafer surfacesin spite of these topographical wafer defects and variations.Chemical-mechanical polishing has gained wide acceptance as an effectivemeans of achieving the global wafer surface planarity required byadvanced devices employing multilayer metalization.

[0008] A typical chemical-mechanical polishing arrangement includes awafer carrier having a generally circular pressure plate or carrierplaten that supports a single substrate or wafer. A carrier film may beinterposed between the carrier platen and the wafer. The wafer carrieris equipped with means to provide a downward force, urging the waferagainst a polishing media (typically a circular pad), onto which is feda polishing fluid. The polishing media is supported by a polishingplaten. The polishing fluid may comprise a colloidal suspension of anabrasive and may also comprise a chemically reactive solution. Acontainment ring generally surrounds the wafer to prevent it fromslipping off the carrier platen during polishing.

[0009] Typically, movement of the wafer relative to the pad, in thepresence of the chemically reactive and/or abrasive polishing fluid andunder pressure imparted by the wafer carrier, imparts a combination ofchemical and mechanical forces to the wafer, the net effect of which isglobal planarization of the wafer surface. Generally, the polishingplaten is rotatable as is the carrier platen. In a typical polishingapparatus, movement of the wafer relative to the pad is accomplished byrotating the polishing platen, the carrier platen, or both.

[0010] Rotating platen machines typically install a circular polishingpad and use it until the pad fails to obtain acceptable results becausethe pad becomes worn or becomes glazed with impacted polishing fluid andpolishing particulate. At that time it is required to interrupt thepolishing process and change the polishing pad. Other machines may use arectangular pad or a continuous supply of polishing pad material thatmay be incrementally advanced over the polishing platen, to ensure thatthe polishing pad is never too worn to be effective.

[0011] Regardless of the configuration of the polishing pad, a commonproblem that occurs when the pad is not fixed to the polishing platenwith an adhesive or other fixing means, is that the polishing padmigrates from its position when polishing forces are applied to it bythe wafer carrier through the wafer. This migration results because thefrictional forces between the wafer and the polishing pad, together withany chemical polishing media that might be employed, are greater thatthe frictional forces that exist between the polishing pad and thepolishing platen. Such migration reduces the productivity and thataccuracy of the polishing process requiring at least a reduction in thepolishing pressure used in the process, thereby increasing the polishingtime. Worse, the polishing pad may buckle during migration, resulting innonplanar polishing results or total failure of the process (e.g.breakage of the substrate). These problems are not solely limited tochemical mechanical polishing but may also occur in purely mechanicalpolishing processes.

[0012] A problem that occurs particularly in chemical mechanicalpolishing machines is depletion of the chemical fluid or slurry betweenthe substrate to be polished, and the polishing pad after a certainamount of polishing motion has occurred. Because of the relativelysmooth and planar surfaces that comprise the polishing pad/platen andthe substrate surface being polished, the polishing action tends to“sweep out” the chemical fluid/slurry and a vacuum or suction builds upbetween the substrate surface being polished and the polishing pad.Thus, this problem gets progressively worse with polishing time.Ironically, the problem also magnifies as the surface of the substratebecomes more planar and smooth, although the problem reduces thepolishing efficiency and performance of the process.

[0013] It would be desirable to have an apparatus with the capability toprevent migration of the polishing pad, while at the same time allowingeasy and quick replacement either continuously or intermittently. Itwould also be desirable to prevent the elimination of the chemicalpolishing agent, e.g., the phenomena known as “slurry starvation”between the substrate surface to be polished and the polishing pad.

DISCLOSURE OF THE INVENTION

[0014] The present invention addresses the above problems, among otheradvantages to be further developed in the following detaileddescription. An apparatus for stabilizing a polishing surface includes asubstantially planar inflexible support base, a flexible polishing padoverlying the support base, and a vacuum port in the support base andunderlying the polishing pad. When vacuum is applied through the vacuumport, the polishing pad is pulled against the support base to maintainthe polishing pad in a predetermined polishing position. A seal ispreferably provided to form a perimeter around the vacuum port on thesupport base. An airtight seal is formed between the support base andthe polishing pad along the seal upon application of the vacuum.

[0015] Another embodiment employs a plurality of vacuum ports to moreevenly distribute the application of vacuum. For example, the pluralityof vacuum ports may lie around a perimeter of the support base.Alternatively, the plurality of vacuum ports may be substantiallyequally distributed over the support base. The plurality of vacuum portsmay include a group of relatively larger vacuum ports around a perimeterof the support base and a group of relatively smaller vacuum portssubstantially equally distributed over an area of the support basewithin the perimeter.

[0016] The present invention further includes the placement of anadditional layer between the polishing pad or media and the supportbase. The additional layer is provided so that, when the polishing padis drawn against the support base by application of vacuum,nonplanarities are formed in the polishing pad. These nonplanaritieshelp retain polishing fluid in the polishing area of the polishing padduring polishing of a substrate.

[0017] The additional layer is preferably a resilient pad. Theadditional layer is perforated so that portions of the polishing pad arepartially drawn into the perforations upon the application of vacuum.Preferably, the perforations have a diameter or size in the range ofabout 0.06 to about 0.25 inches.

[0018] As a means for fixing a polishing pad during polishing, apolishing apparatus according to the present invention includes asubstantially planar inflexible support base, a flexible polishing padoverlying the support base, and means for drawing the polishing padagainst the support base to maintain the polishing pad in apredetermined polishing position. Preferably, the drawing means comprisea vacuum source connected to at least one vacuum port in the supportbase, but other arrangements such as a source to draw the polishing padto the head may be alternatively used as discussed below. Further, asubstrate carrier is movably mounted with respect to the polishing padand the support base.

[0019] A pad may be interposed between the flexible polishing pad andthe support base. Preferably, the pad is perforated or porous. Morepreferably, the pad is a perforated resilient pad.

[0020] Also disclosed is a method of stabilizing a polishing mediaduring polishing of a substrate against the polishing media. The methodincludes providing a polishing media over a substantially inflexiblesupport surface, and applying a vacuum between the support surface andthe polishing media to draw the polishing media toward the supportsurface. The vacuum is applied with a force of about 0.2 to 3.0 psi,preferably about 1.2 psi.

[0021] The method preferably further includes polishing a substrateagainst the polishing media while maintaining the vacuum to determovement of the polishing media with respect to the support surface.Still further, the method may include removing the substrate fromcontact with the polishing media, discontinuing application of thevacuum and removal of the polishing media for cleaning, conditioning orreplacement.

[0022] The method may include replacing the same polishing media aftercleaning and/or conditioning it. After replacing the same polishingmedia, the vacuum is reapplied between the support surface and thepolishing media to draw the polishing media toward the support surface.Alternatively, another polishing media may be positioned on the supportsurface to replace the original polishing media. Once the new polishingmedia is positioned, the vacuum is then reapplied between it and thesupport surface to draw it toward the support surface.

[0023] Optionally, a porous layer may be provided between the polishingmedia and the substantially inflexible support surface prior to applyingthe vacuum. Then, upon application of the vacuum, portions of thepolishing media are partially drawn into porosities of the porous layerto form dimples on a polishing surface of the polishing media.

[0024] An apparatus for stabilizing a polishing surface is disclosed toinclude a substantially inflexible support base; a flexible polishingpad overlying at least a portion of the support base; and a carrier forapplying a substrate against the polishing pad to polish the substrate.Means for maintaining the flexible polishing pad substantially wrinklefree with respect to the substrate may include a vacuum port in thesupport base and underlying the polishing pad, or a mechanism fordrawing the flexible polishing pad against the carrier and thesubstrate, for example.

[0025] When at least one vacuum port is provided in the support base,application of vacuum therethrough pulls the polishing pad against thesupport base to maintain the polishing pad in a predetermined polishingposition. When the means for maintaining includes a mechanism fordrawing the flexible polishing pad against the carrier and thesubstrate, at least one vacuum port may be formed in the carrier. Avacuum source is provided for applying a vacuum between the carrier andthe polishing pad via the at least one vacuum port, thereby maintainingthe polishing pad substantially wrinkle-free, at least in the portionunderlying the carrier and substrate at any given time.

BRIEF DESCRIPTION OF THE DRAWINGS

[0026]FIG. 1 is a partial cross-sectional view of an example of apolishing apparatus and the basic components thereof.

[0027]FIG. 2 is a top view of a first example of the present inventionwhich employs a circular support base.

[0028]FIG. 3 is a schematic view of a polishing apparatus in which apolishing media magazine is employed.

[0029]FIG. 4 is a partial isometric view of a polishing system accordingto another embodiment of the present invention which employs a polishingmedia magazine.

[0030]FIG. 5A is a sectional view of the apparatus shown in FIG. 4 andtaken along line 5-5 with the vacuum applied.

[0031]FIG. 5B is a sectional view of the apparatus shown in FIG. 4 andtaken along line 5-5 when the vacuum is not applied.

[0032]FIG. 6 is a partial view of a variation of the system shown inFIG. 4.

[0033]FIG. 7 is a partial view of a polishing system having anothervariation in the arrangement for applying vacuum to the interfacebetween the support member and the polishing media.

[0034]FIG. 8 is a partial view of a polishing system having yet anothervariation in the arrangement for applying vacuum to the interfacebetween the support member and the polishing media.

[0035]FIG. 9 is a partial view of a polishing system having a variationof FIG. 8, in the arrangement for applying vacuum to the interfacebetween the support member and the polishing media.

[0036]FIG. 10 is a cutaway view of an arrangement of a polishingapparatus which is also adapted toward addressing the problem ofdepletion of the polishing fluid during polishing.

[0037]FIG. 11 is a partial sectional view which illustrates theformation of dimples in the polishing surface of the polishing media.

[0038]FIG. 12 is a partial perspective view of a polishing systemaccording to another embodiment of the present invention.

[0039]FIG. 13 is a view of the support member used in the embodiment ofFIG. 12.

[0040]FIG. 14 is a sectional view of an apparatus employing theprinciples of the system shown in FIG. 12.

[0041]FIG. 15 is a sectional view of another embodiment of a substratecarrier for use in employing the principles of the system shown in FIG.12.

BEST MODE FOR CARRYING OUT THE INVENTION

[0042] Referring to the drawings in detail wherein like numeralsindicate like elements, the present invention generally involvesimprovements to the polishing pad of a polishing apparatus. To betterunderstand the invention outlined below, it is useful to understand thebasic components of the polishing apparatus.

[0043] Referring to FIG. 1, a substrate carrier 120 is generallypositioned over a support base 250 which typically supports a polishingpad or strip 220. Substrate carrier 120 is generally capable ofsupporting a wafer or substrate while supplying the required force tofacilitate polishing. Substrate carrier 120 may have some ability toself align the substrate 260 to the plane of support base 250.Optionally, a resilient pad 240 may be interposed between the polishingpad or polishing media 220 and the support base 250 for improvedpolishing in certain circumstances. The substrate carrier 120 may have aspindle 270 to which the required downward force and rotational forcesare applied. As mentioned above, the substrate carrier 120 is preferablycapable of self alignment so as to align the substrate 260 to thepolishing media 220. Although there are many other possibilities, thesubstrate carrier 120 may allow for the rotation of the lower member 290relative to the upper member 280 about a bearing means 285. Polishingfluid may be applied in metered fashion to the polishing media 220 byway of polishing fluid nozzle 230.

[0044] Various relative motions may be applied between the substrate 260and the polishing media 220 to effectuate a polishing action. Forexample, one type of relative motion is achieved by maintaining thesupport base 250 non-movable with respect to ground and controllablymoving the substrate carrier 120. The substrate carrier may becontrolled by a motion controller (not shown) which is capable ofcontrolled, or programmed movement along directions which are parallelto the plane of the support surface 250. Alternatively or additionally,the substrate carrier may be rotated about the axis defined by thespindle 270. Movement in each of the directions may be, and typicallyis, programmed to occur simultaneously.

[0045]FIG. 2 shows a top view of a first example of the presentinvention which employs a circular support base 150. A flexiblepolishing pad 170 overlies the circular support base 150. An optionalresilient pad (not shown), similar to the resilient pad 240 discussedabove, may be employed between the flexible polishing pad 170 and thesupport base 150. The circular support base 150 may be rotatable so asto effectuate polishing forces against a substrate 260 when thesubstrate is held against the polishing pad 170 by means of a substratecarrier 180. Alternatively, the support base 150 may be held stationarywhile the carrier 180 is moved to effectuate the polishing actionbetween the substrate 260 and the polishing pad 170. The substratecarrier 180 is preferably programmable so as to move linearly,rotationally, or according to a combination of both type movements withrespect to the support base 150 and polishing pad 170.

[0046] Accordingly, there is effectively no limit to the patterns ofpolishing which can be accomplished by the carrier 180 with respect tothe support base 150 and polishing pad 170. Another alternativeoperation of the apparatus shown in FIG. 1 is the simultaneous movementof both the carrier 180 and the support base 150 with respect to oneanother. This would generally involve the rotation of the support base150 while the carrier 180 is also moved rotationally, linearly, or acombination of both types of movement.

[0047] Many conventional polishing apparatuses that have a rotatingsupport base also fix the polishing pad to the support base with anadhesive. Such an arrangement is unwieldy when it comes time to changethe polishing pad due to wear or caking. Removal of the polishing pad isnot easily accomplished and portions of the pad and or adhesive mayremain and require additional attention to ensure that the support baseremains very planar when the new polishing pad is attached. Thus, thiscan be a very tedious and time consuming process that hinders productionby causing down time.

[0048] However, as mentioned above, a common problem that occurs whenthe pad is not fixed to the polishing platen with an adhesive or otherfixing means, is that the polishing pad migrates from its position whenpolishing forces are applied to it by the substrate carrier through thesubstrate. The migration results because the frictional forces betweenthe substrate and the polishing pad, together with any chemicalpolishing media that might be employed, are greater that the frictionalforces that exist between the polishing pad and the support base(polishing platen).

[0049] The arrangement in FIG. 2 overcomes the problems incurred with anadhesively applied polishing pad, as well as the problems mentioned withregard to a pad that is not adhesively fixed. A vacuum port 190 isformed in the support base 150 and connected to a vacuum source (notshown in FIG. 2). For support bases 150 that rotate, the vacuum sourcemay interface with the vacuum port via slip rings or other equivalentarrangements known in the art. A sealing barrier 195, preferably asealing ring such as a strip of IC1000 material (supplied by RODEL), anO-ring or some other material forming an effective vacuum seal,surrounds the vacuum port and follows a contour that is just inside theperimeter of the polishing pad 170. Thus, after positioning thepolishing pad 170 on the support base 150, a vacuum can be drawn throughthe vacuum port 190 which forms an effective air seal along the sealingbarrier 195. Once the air seal is formed, essentially any air existingbetween the polishing pad 170 and support base 150 is removed by thevacuum source thereby effectively fixing the polishing pad 170 to thesupport base 150.

[0050]FIG. 3 shows an embodiment of a polishing apparatus in which it isimpractical to adhesively fix a polishing pad to a support base and inwhich the present invention is all the more important. In thisembodiment, a polishing media magazine 350 is employed rather than anindividual polishing pad 170. The polishing media magazine 350 is shownwith an associated substrate carrier 354 that may be controlled in anyof the movements described above with respect to the carrier 180 in FIG.2. An optional polishing fluid delivery nozzle 352 may supply polishingfluid to the polishing media 310. The polishing fluid delivery nozzle352 may be attached to and move with substrate carrier 354 or may beseparately located or both arrangements may be used. The substratecarrier is shown for illustration purposes only, and may be substitutedby other arrangements such as a substrate carrier driven by linearmotors for example.

[0051] The polishing media magazine 350 preferably uses a polishingmedia 310 that is supplied in the form of a long media roll. Thepolishing media 310 preferably comprises a thin polymeric film substratehaving either a polishing pad or a fixed abrasive covering over at leasta portion of the width thereof. The film may be on the order of 0.001 to0.020 inches thick, preferably around 0.005 to 0.007 inches thick. Thepolishing media 310 should be substantially impermeable to the polishingfluid. Preferably the material is made of Mylar film or polyethyleneglycol terephthalate. New polishing media 310 is preferablyautomatically supplied by the polishing media magazine 350 so that userintervention is not required until the entire roll has been consumed.

[0052] The polishing media 310 may take a variety of paths through thepolishing media magazine depending on the desired configuration andfeatures desired to be interposed within the polishing media path. Thepaths are described in detail in copending U.S. application Ser. No.08/833,278 filed on Apr. 4, 1997 and entitled “Polishing Media MagazineFor Improved Polishing”, which is hereby incorporated by referenceherein in its entirety. In FIG. 3 the media is roll fed from supply roll300 under a first rolling turnbar 320 and across top surface 356 ofplaten support 355. Polishing media 310 exits the top surface 356 over asecond rolling turnbar 325, passes around conditioning system 305,around third turnbar 330 and finally onto take-up roll 340. The thirdrolling turnbar 330 is preferably located at a vertical elevation whichis lower that the take-up roll 340. With this configuration, theresulting angle 359 tends to concentrate the polishing fluid at thirdrolling turnbar 330 for consistent release from the polishing media 310into waste tank 358 as shown.

[0053] A tensioned portion of the polishing media may be positionedaccurately with respect to other features of the polishing mediamagazine by supporting the tensioned portion with precisely placedturnbar elements. These turnbar elements are typically cylindricallyground elongated cylinders or rods supported at each end by bearings.While these rolling turnbars are typically used to reduce overallfriction and wear in the system, other non-rotating elements, such as aporous web roll or porous flotation roll, for example, may be employedto yield the desired polishing media path. Such an example provides atotally now-contact method of transporting the media.

[0054] Whatever the elements that are used to form the polishing mediapath, a tensioned portion is still not entirely resistant to themigration and buckling problems, discussed earlier, that can occurduring polishing. To further fix the tensioned portion in positionduring polishing, polishing apparatuses that employ a polishing mediamagazine may also be employed with a vacuum fixation system according tothe present invention. The present system can be applied to thoseapparatuses regardless of whether they use a slurry or slurry-less typeof polishing media.

[0055] The vacuum system draws a vacuum between the tensioned portion ofthe polishing media and the polishing support surface, to increase theforce with which the tension portion is held in its position. As aresult, the attraction forces between the polishing media and supportsurface are greater than the frictional forces between the between thesubstrate and the polishing media, together with any chemical polishingmedia that might be employed, and no migration or buckling of thepolishing media occurs. This type of solution is not solely limited tochemical mechanical polishing, but may be applied to mechanicalpolishing apparatuses as well. Additionally, the force supplied by thevacuum system may be sufficient to prevent migration or buckling withoutthe need to tension the polishing media.

[0056] In the example shown in FIG. 3, a vacuum source 192 is connectedto a vacuum port 190 that passes through the support 355. Although notshown, a sealing barrier 195 is positioned around the vacuum port 190,similar to that described with regard to FIG. 2 and lying just insidethe perimeter of the tensioned portion of the media 310. the vacuumsource is preferably a high volume, low pressure blower (for example,supplied by GAST, FUJI or AMETEC) that generates about 0.2 to 3.0 psivacuum at the polishing media. A preferred vacuum to be applied is about1.2 psi. A venturi pump may be used to generate about 3-4 psi vacuum tothe media when the media used is thicker than the averages discussedabove.

[0057] A typical operation of the apparatus in FIG. 3 would involveindexing of the media 310 to position a predetermined portion of themedia above the surface 356, tensioning the predetermined portion of themedia 310 above the surface 356, and then applying vacuum via the vacuumsource 192. Upon forming a seal between the media 310 and the surface356 via the sealing barrier, the vacuum would then evacuate all airexisting between the media 310 and surface 356 at which time the mediawould become essentially fixed to the surface 356. Polishing operationscan next be commenced. The vacuum is preferably maintained until amovement of the media is desired, whether for conditioning or cleaningpurposes or to advance to a new portion of the media to be used forpolishing.

[0058]FIG. 4 is a partial view of a polishing system according toanother embodiment of the present invention. The polishing media 310passes over roller 420, but this is of no consequence to the presentinvention. In this embodiment the longitudinal edges of the supportsurface underlying the polishing media 310 are raised in height withrespect to the remainder of the support surface by movable edge elements465. Although not stated above, the longitudinal edges of the surface356 may optionally be raised with respect to the remainder of thesurface 356, however the edges are integral with the remainder ofsurface 356. The media 310 need only have a working area for polishingas wide as the planar section between the raised edge sections. The areaoutside of the working width need not be coated, thus saving materialexpense.

[0059] The raised edge portions aid in creating raised edges of thepolishing media 310. For embodiments that use a slurry in the polishingprocess, the raised edges aid in maintaining the slurry in the polishingarea and in channeling the slurry to an appropriate receptacle foreither recycling or disposal. More important to the present invention,the raised edges also urge the media 310 against the sealing barrier tomake sure that a vacuum can be reliably drawn upon application of vacuumto the system through the vacuum source 192.

[0060] The movable edge elements 465 are particularly effective inmaintaining close positioning of the sealing barrier 495 with thepolishing media 310 as shown in FIGS. 5A-5B. The edge elements 465 arevertically biased upwardly with respect to the support member 455 bybiasing elements 468, as shown in FIG. 5B. The biasing elements 468 arepreferably springs, most preferably a type of coil springs, but othersprings with equivalent biasing characteristics may be readilysubstituted, as may other resilient biasing mechanisms such as o-rings,bladders, pneumatic or hydraulic devices, etc.

[0061] Upon application of vacuum through the vacuum port 190, a seal isformed between the media 310 and sealing barrier 495. The media is thendrawn flat against the support surface 465 and secured there by thevacuum pressure as shown in FIG. 5A. Note that the vacuum force isenough to overcome the biasing force of the biasing elements 468, whichare compressed and the edge elements 465 are depressed into theirlowermost vertical position as they bottom out when the biasing elements468 become fully depressed, as shown in FIG. 5A. In their lowermostpositions, the edge elements 465 align the polishing media 310 to ensurea smooth and flat interface over the entirety of the planar polishingsurface 465 that the edge elements 465 border.

[0062] Upon release of the vacuum, the biasing force of the biasingelements becomes greater than the minimized downward force of the media310. As a result, the edge elements 465 are biased into their uppermostpositions as shown in FIG. 5B. By assuming the uppermost positions, theedge elements ensure that the sealing barrier along the longitudinaledges remains in contact with the media 310 when the vacuum is lacking,as also shown in FIG. 5B. This greatly improves the reliability of thesystem in ensuring that a vacuum can be drawn once again at the desiredtime.

[0063] The partial view of a polishing system 550 shown in FIG. 6 showsa variation in the arrangement for applying vacuum to the interfacebetween the support surface 456 of the support member 455 and thepolishing media 310. In this arrangement, a plurality of vacuum ports290 are spaced along the surface 456 just inside the perimeter definedby the sealing barrier 495. In the example shown, the vacuum ports 290are evenly distributed and are of equal size. However, the invention isnot to be so limited. The distribution of vacuum ports may be moreconcentrated, for example along the width edges to compensate for thelack of elevated edges in these areas. Alternatively, or in additionthereto, the vacuum ports may be of unequal size in different locationsto tailor the application of vacuum as preferred. Also, many smallvacuum ports could be distributed throughout the surface 456 toaccomplish a secondary objective of assisting in the prevention ofslurry/liquid starvation, which will be discussed in more detail below.

[0064]FIG. 7 shows a partial view of a polishing system 650 havinganother variation in the arrangement for applying vacuum to theinterface between the support surface 556 of the support member 555 andthe polishing media 310. In this arrangement, a plurality of very smallvacuum ports 390 up to a quarter of an inch (0.25″), preferably up to aneighth of an inch (0.125″) are distributed over the entire working area(i.e., area underlying the tensioned portion of the polishing media andlying within the boundary of the sealing barrier 495) of the surface556. In the example shown, the vacuum ports 290 are substantially evenlydistributed and are of substantially equal size. However, the inventionis not to be so limited. The distribution of vacuum ports may be moreconcentrated, for example near the perimeter of the surface adjacent thesealing barrier 495. Alternatively, or in addition thereto, the vacuumports may be of unequal size in different locations to tailor theapplication of vacuum as preferred. For example, the vacuum ports may belarger along the inside of the perimeter of the sealing barrier 495, ascompared to the vacuum ports further inside the sealing barrier (closerto the center of the surface 556).

[0065] All of the foregoing embodiments may be constructed so as to haveelevated, integral longitudinal edges, movable elevated edge elements,or edges which are coplanar with the remainder of the support surface.

[0066]FIG. 8 shows a partial view of a polishing system 475 havinganother variation in the arrangement for applying vacuum to theinterface between the support surface 478 of the support member 476 andthe polishing media 310. In this arrangement, a groove or channel 477 isformed into the support surface 478 generally around the peripherythereof, but inside the bounds of the sealing barrier 495. A vacuumsource (not shown, but like described with regard to FIG. 3) isconnected to the channel 477 via a vacuum port 479 that passes throughthe support 476.

[0067] Upon application of the vacuum, existing air, between thepolishing media 310 and portion of the polishing surface 478 lyinginside the sealing barrier 495, is evacuated through the channel 477 andport 479 so as to draw the polishing media 310 against the polishingsurface 478 to securely hold the polishing media in position during thepolishing process. In the example shown, the channel 477 issubstantially uniformly dimensioned around the entire periphery thereof.However, the invention is not to be so limited, as the channel can beformed to be wider or deeper in select areas such as the corners or endsof the rectangular pattern shown. Also, the channel can be formed inother configurations, such as oval, hourglass, etc.

[0068]FIG. 9 shows another variation that may be practiced using vacuumchannels. In this embodiment, an additional channel 487 is formedinteriorly of the perimeter established by the channel 477. The twochannels 477 and 487 are connected by a connecting port 488 which liesbeneath the polishing surface 489. Alternatively, a channel could beformed in the polishing surface 489 to connect the channels 477 and 487,but a port 488 is preferred. Since the channel 487 will generally liemore in the path of polishing, it is preferable, but not necessary, toform the channel 487 to be narrower than channel 477, so as not tosignificantly disrupt the planarity of the polishing surface. A port 491connects the channels 477,487 and port 488 to a vacuum source (notshown).

[0069] All of the foregoing embodiments may be constructed so as to haveelevated, integral longitudinal edges, movable elevated edge elements,or edges which are coplanar with the remainder of the support surface.

[0070]FIG. 10 is a cutaway view of an arrangement of a polishingapparatus which is also adapted toward addressing the problem ofdepletion of the chemical fluid or slurry or other fluid which is usedbetween the substrate to be polished and the polishing pad duringpolishing. As referred to above, after a certain amount of polishingmotion has occurred, this fluid tends to become more and more depleteduntil there is virtually no fluid between the substrate and polishingpad. Because of the relatively smooth and planar surfaces that comprisethe polishing pad/platen and the substrate surface being polished, thepolishing action tends to “sweep out” the chemical fluid/slurry and avacuum or suction builds up between the substrate surface being polishedand the polishing pad.

[0071] The polishing apparatus 750 includes a porous, resilient layer710 between the polishing media 310 and the support surface 556. Whenvacuum is applied via the vacuum port 190, the polishing media 310 isforced toward the support surface 556 with a force sufficient to atleast partially compress the resilient layer 710. The thin polishingmedia is further drawn against the resilient layer 710 and partiallyinto the porosities 720 within the resilient layer 710 as air isdepleted from the porosities. The result is that a plurality ofconcavities or “dimples” are formed in the polishing surface of thepolishing media 310. A partial sectional view of the relationshipbetween the support 555, resilient layer 710, polishing media 310 andsubstrate 260 is diagrammed in FIG. 11.

[0072] Concavities 810 in the polishing media 310 are formed over theporosities 720 of the resilient layer 710 when the vacuum is applied asdescribed above. the concavities act as capacitances for slurry, KOH,water, or whatever liquid medium 840 is used during the polishingprocess. Thus, even when a very planar substrate 260 passes over thepolishing media 310, not all of the fluid 840 is swept out of thepolishing area. Rather, pockets of fluid/polishing medium remain in thedimples 810 to help prevent slipping/sticking (e.g., “stiction”)problems that are often observed as a result of slurry/fluid starvationbeneath the substrate to be polished.

[0073] A preferred resilient layer is the IC1000 pad supplied by RODEL,although other available equivalent porous and resilient materials maybe substituted. Alternatively, relatively non-resilient layers having aporosity similar to IC1000 may be successfully used for dimple formationin the polishing media 310. Still further, dimples may be formed in thepolishing media 310 if the layer between the polishing media 310 andsupport surface 555 is left out altogether, when the support surface 556is provided with vacuum ports 390, similar to those shown in FIG. 7,that are close to the pore size of IC1000.

[0074]FIG. 12 is a partial view of a polishing system according toanother embodiment of the present invention. The polishing media 310passes over rollers 420 and 325 as in previous embodiments, but, as inthe previous embodiments, this is of no consequence to the presentinvention, as the present invention may be practiced with other mediaarrangements, e.g., a single flexible sheet of polishing media. In thisembodiment the support surface 856 of the support member 855 is hollowedout or at least recessed in the central portion 857 thereof (see alsoFIG. 13).

[0075] The edge surfaces 858 support the polishing media 310 and thepolishing media is preferably tensioned over the surface 855 and clampedto the edge surfaces 858 by clamps 870 with or without the applicationof vacuum to the periphery of the polishing media, preferably with. Themedia is preferably tensioned to at least 2 lbf per inch of media width.Preferably the clamping is performed near the four corners of the tableusing four clamps 870 as shown, but more or fewer clamps may be used.Alternatively, the media may be clamped along the entire edge thereofalong both side using long clamps the surfaces of which are extended byan underlying foam or other soft tapering substance.

[0076] The substrate carrier 860 is provided with at least one vacuumport 865 preferably in an area surrounded by the containment ring 868 orother structure outlying the substrate 260. The vacuum port 865 isconnected to a vacuum source 880 via a vacuum tube 890. As in theprevious embodiments, this embodiment is not limited to the use of asingle vacuum port, but alternative arrangements may include multiplevacuum ports of equal or unequal size, variously spaced around theperimeter of the ring area. Preferably, when a multitude of vacuum portsare employed, the vacuum ports are equally spaced about the ring area,but this is also not absolutely necessary.

[0077] At least one sealing barrier 866 is provided around the perimeterof the substrate carrier 860, preferably very close to the edge of thecarrier 860 and necessarily surrounding the vacuum port(s) 865.Preferably, the surface of the containment ring 868 that contacts thepolishing media 310 functions as the sealing barrier 866. Optionally, adedicated sealing barrier may be positioned either on the containmentring contacting surface, or adjacent the inside circumference of thecontainment ring 868. Upon application of vacuum through the vacuum port865, a seal is formed between the media 310 and sealing barrier 866. Themedia is then drawn flat against the substrate 260 and bottom surface ofthe substrate carrier 860 and secured there by the vacuum pressure drawnthrough vacuum port 865.

[0078] Polishing of the substrate may next be commenced. Pressureapplied by the substrate carrier 860 against the substrate 260 worksagainst the vacuum force that draws the media 310 against the surface ofthe substrate 260 to be polished, thereby providing the working pressureneeded to polish the substrate (i.e., the “P” variable in Preston'sequation). One advantage of this arrangement is that an absolutely flat,planar polishing or support surface is not required. Additionally, amuch lighter weight support member 855 is possible due to the recessedor hollow central portion that does not need to be capable of providinga support against which the polishing will take place.

[0079] Upon release of the vacuum, the biasing force of the tensionedmedia 310 becomes greater than any attractive forces that might possiblyremain between the media 310 and the substrate 260 and carrier 860. As aresult, the media 310 withdraws from contact with the substrate 260 andsubstrate carrier 860 and resumes a substantially planar configurationwhich is substantially coplanar with support 855. An optional featuremay be provided on carrier 860 to provide a positive force such aspositive fluid pressure (preferably air) against the media 310 afterrelease of vacuum pressure to assist in separating the media 310 fromthe substrate 260 and carrier 860.

[0080] The carrier 860 is then elevated from the media 310 to enableeasy removal of the substrate 260 for inspection and/or replacement.Once a substrate is repositioned between the media 310 and carrier 860,the carrier 860 is repositioned near or against the media 310.Reapplication of vacuum produces a seal as described above, at whichtime polishing is recommenced.

[0081]FIG. 14 is a sectional view of a system using the vacuumtechniques described above with respect to FIGS. 12 and 13. Also shownis an embodiment of a substrate carrier 860. The plate 955 of thesubstrate carrier 860 forms an upper reference plane from which theforce application means 960 apply the load to the substrate 260. In thisexample, the force application means include three concentric rings 961,962 and 963 which are configured to emit controlled flows of gas and/orliquid. Preferably, the application means 961, 962 and 963 emit air toform a pressurized air layer 970 between the plate 955 and the substrate260. However, other gases, water, a mixture of water and air and/orother gases, or vacuum may also be employed in forming a bearing orfixation layer 970 between plate 955 and substrate 260. Of course, thistype of carrier is not limited to the use of three rings, but may usefour rings or more, or even one or two rings.

[0082] In the embodiment shown, pressure lines 964, 965 and 966 connectthe rings 961, 962 and 963, respectively to a source of pressurized air(not shown). Throttle valves 967 are provided on each of the lines toenable an operator to independently regulate the flow through each ofthe rings 961, 962 and 963 while using a single pressure input line 968.A more detailed and complete description of such a carrier is set forthin a co-pending application entitled “Padless Substrate Carrier” filedon even date herewith and bearing Attorney's Docket No. 36172-20017.00.The aforementioned “Padless Substrate Carrier” application is herebyincorporated by reference thereto in its entirety.

[0083] Optionally, slurry lines 972 may pass through the drive plate971, to allow continuous or otherwise automatically controlled feedingof slurry for systems employing a slurry with the polishing media. Thepresent invention is not limited to use with the carrier described inFIG. 14, but may be used with more conventional carriers, includingthose that employ a substrate backing pad, and those that rotate. Otherdesigns, such as those with bladder-filled, conformable crowns and otherpressure arrangements for conforming the crown of a carrier, may also beused.

[0084] In the embodiment of FIG. 14, flow through the rings 961, 962 and963 may be set to deliver an equal flow rate/pressure of air/liquid, ora constant pressure profile or both may coincide. Additionally, theoutermost ring 961 can be formed very close to the edge of the faceplate955 to enable the pressure wave to extend at a substantially constantvalue nearly to the edge of the faceplate. The bearing layer 970 furtherenables the substrate to “float” or precess with respect to thefaceplate 955, since the faceplate 955 does not contact the backside ofthe substrate once the layer 970 has been formed. The radius of thesubstrate 260 is somewhat smaller than that of the faceplate, and thesubstrate is maintained in position between the faceplate 955 and thepolishing media 310 by the presence of containment ring 868.

[0085] The combination of the ability to apply substantially uniformload pressure over the entire surface of the backside of the substratewith the ability to allow the substrate to precess or float within theconfines of the containment ring results in a very uniform polishingprocess that removes material consistently from the edge of thesubstrate to the center.

[0086] Alternatively, in situations where shaping or conformation of thepressure profile is required, the flow through the rings 961, 962 and963 can be varied to achieve the desired conformation of the pressureprofile.

[0087] During polishing with the arrangement of FIG. 14, in addition tothe application of force by applicators 960 by the carrier as describedabove, the vacuum applied through 890 to the polishing media and withinthe carrier 860, draws the polishing media 310 against the substrate260, and is held in position there by the force of atmospheric pressurePa pressing against the polishing media 310 on the back side thereofwith uniform pressure, while the back surface of the substrate 260 issupported by fluid/air pressure supplied by the carrier 860, or byvacuuming the substrate to the carrier through a full porous sheet, forexample.

[0088] Advantageously, this arrangement requires no vertical forceapplication of the carrier 860 against the support 856. Thus, the driveplate 971 only needs to provide horizontal force during polishing. Noris a precision polishing surface required, since the actual polishingaction is accomplished out of contact with the support 856, with thepolishing media 310 being pressed against the polishing surface of thesubstrate 260. This greatly reduces the required weight of the polishprocessing machine as well as reducing the cost of the support 856.Additionally, since the support 856 may be made much less bulky and lessheavy, this enable multiple units or modules to be stacked much moreeasily, for parallel processing of substrates. Such modules may bestacked or oriented with the polishing surface of the wafer in ahorizontal configuration facing up, in a horizontal configuration facingdown, or in a vertical or other “off-horizontal” configuration.

[0089] Another optional feature of the carrier 860 is the provision of afaceplate 955 which is formed out of a transparent material, such aspolycarbonate with an electrostatic film on the surface thereof, forexample. The provision of a transparent faceplate 955 allows an observerto confirm that the substrate is properly precessing during polishing.

[0090]FIG. 15 is a sectional view of another preferred embodiment of asubstrate carrier 1060 which uses vacuum both for control of thesubstrate extension by the carrier plate, as well as to supply afixation force for holding the substrate against the carrier. In thisarrangement, the carrier plate 1155 is mounted to a carrier loadingcolumn 1110, via seal plate 1120 and carrier plate down stop 1172extending from containment ring support 1170. A diaphragm 1140 ismounted between the seal plate 1120 and the carrier plate 1155 to form apressurizable chamber 1145.

[0091] The location of the carrier loading column 1110 forms the basisfor gross positioning of the carrier. The location of the carrierloading column 1110 provides the primary load control of the containmentring 1180 which provides side load bearing control of the substrateduring polishing.

[0092] A vacuum source 1130 is connected to a second pressurizablechamber 1134 via main vacuum lines 1132, which are connected to vacuumholes 1147 in the containment ring support 1170. Vacuum wafer pick upholes 1182 in the carrier plate 1155 are connected to an independentlycontrollable vacuum/pressure source (not shown) via manifold 1184 whichis joined to at least one vacuum port 1166 by vacuum tubing and fixtures(not shown). The application of vacuum through vacuum holes 1182 fixesthe back side of a substrate against the carrier plate 1155. In thisexample, four rings of vacuum holes are provided in addition to a vacuumhole centrally located through the face 1155′ of carrier plate 1155,although other configurations of vacuum holes could be alternativelyused. Additionally, monitoring holes 1192 may be provided intermediatethe vacuum hole 1182 arrangements to be used for monitoring the pressureand/or flow at the locations of their placement. The monitoring holesmay be independently connected to individual monitoring pressure/flowsensors (not shown) or may be connected to a central sensing unit (notshown) though manifold 1194.

[0093] A differential vacuum line 1160 connects with pressurizablechamber 1145 and an orifice 1162 is provided at an opposite end ofvacuum line 1160 which is exposed to atmospheric pressure. A valve 1164,preferably a bleed valve, interconnects the main vacuum line 1132 andthe differential vacuum line 1160. The valve 1164 may be adjusted so asto close off the differential vacuum line 1160 to the vacuum source1130, in which case the pressurizable chamber 1145 will assumeatmospheric pressure via the orifice 1162. This relatively high pressureexpands the pressurizable chamber to drive the diaphragm 1148 and thusthe carrier plate 1155 and face 1155′ downward in FIG. 15, whicheffectively provides a greater polishing force on the substrate. Carrierplate down stop 1172 prevents overextension of the carrier face 1155′ inthe downward direction by limiting the downward movement of the carrierplate 1155.

[0094] The valve 1164 may be adjusted so as to open the differentialvacuum line 1160 to the vacuum source 1130 and to variably adjust theamount of flow, in which case the pressurizable chamber 1145 will assumepressure values less than atmospheric pressure. This contracts thepressurizable chamber to draw the diaphragm 1148 and thus the carrierplate 1155 upward in FIG. 15, which effectively provides a lesserpolishing force on the substrate. The degree of upward movement iscontrollable by varying the flow through adjustments of the valve 1164as referred to above.

[0095] During polishing with this arrangement, similar to thearrangement of FIG. 14, vacuum is also applied to the polishing media todraw the polishing media 310 against the substrate 260, and thepolishing media is held in position by the force of atmospheric pressurePa pressing against the polishing media 310 on the back side thereofwith uniform pressure, while the back surface of the substrate 260 isheld by the vacuum applied through the carrier faceplate 1155′, asdescribed above.

[0096] Similar advantages to those discussed with regard to theembodiment in FIG. 14 also exist with regard to this embodiment. Inorder to control the generation of heat that ensues from the abrasion ofthe substrate and the frictional forces between the substrate and thepolishing media, misters or air sprayers may be used to apply one ormore flows of cooling streams against the backside of the polishingmedia 310, i.e., the side which does not directly contact the substrate.Alternatively, a water bed may be provided in contact with the backsideof the polishing media 310.

[0097] It may also be desirable to provide a more rigid backing on thepolishing media 310 by vacuuming a thin polycarbonate sheet (e.g., about0.060 inches thick) to the backside of the media. Alternatively,stiffness could be increased by simply increasing the thickness of thepolishing media itself. Additionally or alternatively, the backing sheetmay be slit with grooves on the side which contacts the back side of thepolishing media to enhance uniformity and planarization of thesubstrate.

EXAMPLES

[0098] 1. A polishing support surface is provided with a substantiallyrectangular sealing barrier having dimensions of about 22″×19″. A singlevacuum port is provided centrally and at one end of the polishingsurface defined within the perimeter of the sealing barrier. By applyinga vacuum pressure of about 2 psig, the approximately 418 in² providesapproximately 836 pounds of attractive force to a polishing media thatoverlies the support surface and which makes a vacuum seal with thesealing barrier. This extra load eliminates stretch, migration andbuckling of the polishing media, and may be used to eliminate the needfor tensioning of the polishing media. The polishing media is a MYLAR™film having a fixed abrasive on the polishing area thereof, and issupplied by 3M Company or DuPont.

[0099] 2. In addition to the same conditions as in (1) above, an IC1000layer is positioned as a subpad beneath the polishing media and abovethe support surface. When the vacuum is applied through the vacuum port,the polishing area of the polishing media is drawn down against thesubpad and the support surface. Air is depleted from the spaces betweenthe polishing media, subpad and support surface, causing a compressionof the subpad and also causing the portions of the polishing mediaoverlying the pores of the subpad to be partially drawn into the pores.As a mixture of KOH and water is supplied to the polishing surface ofthe polishing media, the polishing operation is commenced. Movement ofthe wafer carrier, wafer retaining ring and the wafer against thepolishing media tends to sweep out the KOH/water polishing solution fromthe polishing area.

[0100] However, dimples in the polishing media, which were formed by theportions of the polishing media overlying the pores of the subpad beingpartially drawn into the pores of the subpad by the vacuum, trap smallpools of the KOH/water polishing fluid thereby making the polishingfluid continuously available to the wafer surface being polished.

What is claimed is:
 1. An apparatus for stabilizing a polishing surfacecomprising: a substantially planar inflexible support base; a flexible,advanceable polishing pad overlying the support base; and a resilientpad interposed between the polishing pad and the support base, theresilient pad being at least one of perforated and porous; one or morevacuum ports disposed in the support base and underlying the polishingpad, wherein application of vacuum through the one or more vacuum portspulls the polishing pad against the support base to maintain thepolishing pad in a predetermined polishing position; and a seal forminga perimeter around the one or more vacuum ports on the support base,wherein an airtight seal is formed between the support base and thepolishing pad along the seal upon the application of vacuum.
 2. Theapparatus of claim 1, wherein the seal assembly further comprises asealing barrier, a movable edge element, and a biasing element.
 3. Theapparatus of claim 1, wherein the one or more vacuum ports lie around aperimeter of the support base.
 4. The apparatus of claim 1, wherein theone or more vacuum ports are substantially equally distributed over thesupport base.
 5. The apparatus of claim 1, wherein the one or morevacuum ports includes a group of relatively larger vacuum ports around aperimeter of the support base and a group of relatively smaller vacuumports substantially equally distributed over an area of the support basewithin the perimeter.
 6. The apparatus of claim 1, wherein theperforated pad comprises perforations having a diameter less than about0.25 inches.
 7. The apparatus of claim 1, wherein the support basefurther comprises a first groove formed therein, the first groovecoupled to the vacuum port.
 8. The apparatus of claim 7, wherein thesupport base further comprises a second groove formed therein.
 9. Theapparatus of claim 8, wherein the support base further comprises a thirdgroove formed therein, the third groove intersecting the first and thesecond groove.
 10. The polishing apparatus of claim 1, furthercomprising a substrate carrier movably mounted with respect to thepolishing pad and the support base.
 11. A method of stabilizing apolishing media during polishing of a substrate against the polishingmedia, comprising: providing an advanceable polishing media over asubstantially inflexible support surface; providing at least one of aporous and a perforated layer between the polishing media and thesubstantially inflexible support surface prior to said applying thevacuum; and applying a vacuum between the support surface and thepolishing media to draw the polishing media toward the support surface;and polishing a substrate against the polishing media while maintainingthe vacuum to deter movement of the polishing media with respect to thesupport surface.
 12. The method of stabilizing of claim 11, wherein thevacuum is applied with a force of about 0.2 psi to 3.0 psi.
 13. Themethod of stabilizing of claim 12, wherein the vacuum is applied with aforce of about 1.2 psi.
 14. The method of claim 11, further comprising:removing the substrate from contact with the polishing media;discontinuing application of the vacuum; and removal of the polishingmedia for cleaning, conditioning or replacement.
 15. The method of claim14, further comprising: replacing the polishing media after cleaning,conditioning, or both; and applying a vacuum between the support surfaceand the polishing media to draw the polishing media toward the supportsurface.
 16. The method of claim 14, further comprising: positioninganother polishing media on the support surface; and applying a vacuumbetween the support surface and the another polishing media to draw theanother polishing media toward the support surface.
 17. The method ofclaim 11, further comprising: removing the substrate from contact withthe polishing media; discontinuing application of the vacuum; andrepositioning the polishing media with respect to the support surface.18. The method of claim 17, further comprising reapplying the vacuumbetween the support surface and the polishing media to draw thepolishing media toward the support surface.
 19. The method of claim 11,wherein, upon the applying the vacuum, portions of the polishing mediaare partially drawn into porosities of the porous layer to form dimpleson a polishing surface of the polishing media.
 20. The method of claim11, wherein the applying step further comprises applying the vacuumthrough one or more grooves disposed in the support surface.
 21. Themethod of claim 11, wherein the applying step further comprises applyingthe vacuum through two or more interconnected grooves disposed in thesupport surface.
 22. An apparatus for stabilizing a polishing surfacecomprising: a substantially inflexible support base; a flexible,advancable polishing pad overlying at least a portion of said supportbase; a carrier for applying a substrate against said polishing pad topolish the substrate; and means for maintaining said polishing padsubstantially wrinkle free with respect to the substrate.
 23. Theapparatus of claim 22, wherein the means for maintaining comprises amechanism for drawing the flexible polishing pad against the carrier andthe substrate.
 24. The apparatus of claim 23, wherein the mechanismcomprises at least one vacuum port in the carrier and a vacuum sourcefor applying a vacuum between the carrier and the polishing pad via theat least one vacuum port.
 25. A method of polishing a substrate betweena substrate carrier and a polishing medium, comprising: pressing thepolishing medium against a surface of the substrate to be polished byapplying vacuum between the substrate carrier and the polishing mediumso that atmospheric pressure presses the polishing medium against thesubstrate and substrate carrier; supporting the substrate with thecarrier against a surface of the substrate which is not to be polished;and imposing relative movement between the polishing medium and thesubstrate by moving at least one of the polishing medium and thesubstrate.
 26. The method of claim 25, wherein the supporting comprisesestablishing a fluid bearing between the substrate carrier and thesubstrate.
 27. The method of claim 26, wherein the fluid bearingcomprises an air bearing.
 28. The method of claim 25, wherein thesupporting comprises establishing fixation between the substrate carrierand the substrate.
 29. The method of claim 28, wherein the fixation isestablished by drawing a vacuum between the substrate carrier and thesubstrate.
 30. A polishing apparatus comprising: a flexible polishingpad adapted to contact a front surface of a substrate to be polished; asubstrate carrier adapted to support a back surface of the substrate;and at least one vacuum port on the substrate carrier adapted to applyvacuum against the flexible polishing pad, thereby pressing thepolishing pad against the substrate to be polished and the substratecarrier.
 31. The apparatus of claim 30, further comprising at least oneport in a face of the substrate carrier for establishing a fluid bearingbetween the substrate carrier and the substrate.
 32. The apparatus ofclaim 30, wherein the at least one port in the face is adapted toestablish an air bearing between the face and the substrate.
 33. Theapparatus of claim 30, further comprising at least one port in a face ofthe substrate carrier for establishing fixation between the substratecarrier and the substrate.
 34. The apparatus of claim 33, wherein the atleast one port in the face is adapted to draw a vacuum between thesubstrate carrier and the substrate.
 35. The apparatus of claim 34,further comprising a vacuum source connected to the at least one port inthe face.
 36. An apparatus for stabilizing a polishing media comprising:a substantially planar inflexible support base having a top surface; anadvanceable polishing media over a substantially inflexible supportsurface; a means for drawing the polishing media against the supportsurface; and at least two rolling turnbar elements wherein a tensionedportion forms straight-line tangent segments between the turnbarelements.
 37. The apparatus of claim 36, further comprising: a polishingmedia supply roll and a polishing media take-up roll, wherein thetensioned portion extends from the supply roll to the take-up roll. 38.The apparatus of claim 36, wherein a portion of the tensioned portionpasses around a conditioning system.
 39. The apparatus of claim 38,wherein another portion of the tensioned portion passes around a thirdrolling turnbar element, the third turnbar positioned vertically lowerthan the take-up roll forming an angle adapted for consistent release ofthe polishing media into a waste tank.